metastoma

noun3

1. •
   A median elevation behind the mouth in the arthropods.
2. •
   A ventral single plate located in the opisthosoma of some non-arachnid chelicerates in the extinct genus Houia which is involved in feeding and manipulating food.
3. •
   A structure found in some mosses and liverworts that covers the mouth of the capsule from which spores are released.